The overall objective of the proposed research is to continue to use the estrogen induced and -dependent renal carinoma of the hamster as a model to study estrogen carcinogenicity, dependency of these carcinomas on hormones, and the transition of these tumors from hormone dependency to autonomy. Pertinent is the relationship between estrogen carcinogenesis and the steroid receptor system. The presence of a 4 S estrogen binder in the hamster kidney together with its increased quantities in DES treated animals as evidenced by the appearance of an 8 S moiety and the markedly increased levels of progesterone receptor as a result of estrogen treatment during the period of estrogen renal tumorigenesis remains to be defined. Our demonstration that all of the major classes of steroid receptors are present in the hamster carcinoma and its metastases in appreciable quantities provide a unique system to study both in-vivo and in-vitro the harmonal interrelationships involved in tumor response to endocrine therapy as well as the interrelated actions of steroid hormones within a single tissue. Therefore, the multiple steroid hormone receptors found in the hamster renal carcinoma should be a useful model in understanding hormone dependence and responsiveness of such human carcinomas as cancer of the breast and endometrium in which multiple steroid receptors are established clinical findings. Since estrogen carcinogenesis in the hamster is not complicated by other carcinogens or hormonal factors, insight should be gained into the nature of estrogen as a carcinogen. To assess the possible therapeutic application of steroid hormones in the human renal carcinoma, the presence of steroid receptors will be assessed in terms of their frequency of occurrence and concentration.